NA TURE 



{Sept. 1 8, ii 



goods. I shall try to forward collections addressed to you by 

 every mail if feasible. Then, if you judge of the value, and 

 estimate that my share of the collections will realise a good 

 amount, it will induce me to devote more time to the country. 

 My health, notwithstanding a much mure trying climate than' I 

 have yet met with in Africa, has been very good, and I have 

 not known an hour's illness or indisposition. Sir John Kirk has 

 shown me the utmost kindness and hospitality, and his help and 

 his influence have smoothed away many difficulties 'Mil i 

 pedition promises most favourably, as the present condition of 

 the countries to be traversed is good and peaceful, food abun- 

 dant, and provisions cheap I have obtained the services 



of three of Dr. Fischer's bird-skinners, and have got one botani- 

 cal collector, trained under Sir John Kirk, and acquainted with 

 the mysteries of 'soldering' and preserving in spirit. I have 

 sent for rectified spirit from Bombay, and in the interval am 

 using trade gin. The Sultan has given me three kegs of gun- 

 powder to give as presents to chiefs, and has also furnished me 

 with letters of introduction. I am in excellent condition, and 

 start to-day on my journey in the best spirits and with the 

 strongest hopes of its success," 



Refo>t of the Committee, consisting of Mr. James N. Shool- 

 bred (Secretary} and Sir William Thomson, appointed for the 

 Purpose of Reducing and Tabulating the Tidal Observations in 

 the English Channel made with the Dover Tide-Gauge, and of 

 Connecting them with Observations made on the French Coast. 

 — The Committee beg to report that the tidal curves of the self- 

 registering tide-gauge at Dover for the years 1SS0, 18S1, 1882, 

 and 1883, have been kindly placed at their disposal by the Board 

 of Trade, for reduction and tabulation ; and that the Belgian 

 Government have been good enough to present to the Com- 

 mittee copies of the tidal curves at Ostend during the sanre 

 period of four years. The reduction and tabulation of the high 

 and low water registers of these two sets of tidal curves has pro- 

 gressed satisfactorily, and will be shortly completed. It is hoped 

 also that a like reduction will be soon commenced with other 

 self-registering tidal curves during the same period at several 

 other points, both on the English and the French coasts. The 

 Committee request to be allowed to transmit to the Board of 

 Trade and to the Belgian Government respectively, the thanks 

 of the Association for their assistance and donations in further- 

 ance of this inquiry. The Committee request to be re- 

 appointed, with a grant of lot. to defray the expenses of 

 reduction, &c. 



Report of the Committee, consisting of Prof. Balfour Stewart 

 (Secretary), Prof. Stokes, Mr. G. Johnstone Stoney, Prof. 

 Roscoe, Prof. Schuster, Capt. Abney, 'and Mr. G. /. Symons, 



appointed for the Purpose of Considering the Best 'Methods of 

 Recording the Direct Intensity of Solar Radiation. — This Com- 

 mittee, acting on a suggestion made by Gen. Strachey, have 

 chiefly devoted their attention to the subject of a self-recording 

 actinometer. The self-recording actinometer of Mr. Winstanley 

 would not be suitable, 1 because it is influenced by radiation 

 from all quarters. Other actinometers require manipulation on 

 the part of the observer which would make it almost impossil 1 

 to make them self-recording. It was suggested by Prof. Balfour 

 Stewart that a modification of his actinometer might be adapti d 

 to self-registration by taking for the quantity to be observed. I 

 not the rise of temperature of the inclosed thermometer after 

 exposure for a given time, but the excess of its temperature 

 when continuously exposed over the temperature of the envelope. 

 After making some calculations as to the behaviour of such an 

 instrument, Prof. Stokes came to the following conclusions :— 

 (1) The inclosure should be of such a nature as to change its 

 temperature very slowly, and of such a material that the vaiiou, 

 portions of the interior should be at the same moment of the 

 same uniform temperature. For this purpose an arrangement 

 somewhat similar to that used in Prof. Stewart's actinometer is 

 suggested ; the outside to consist of polished metallic plates, 

 then a layer of some non conducting substance, such as felt, 

 then a thick coj per interior which netd not be polished. Into 

 this copper is to be inserted a thermometer which will give the 

 temperature of the copper interior from moment to moment. 

 _ t "This is the case at present, but there would not be any great difficulty 

 in modifying it so as to act as required. It is quite a matter worth con'. 

 sideration whether a differential air-thermometer would not be very suitable, 

 one bulb silvered and the other blackened or of gr<en glass, as I suggested 

 to the Meteorological Council some years back. By this means only mm 

 reading would be necessary, whilst in the plan suggested two would have to 

 be recorded, .-,,..1 the uv.isiirvnients would be more difficult." (Note by 

 > ■ I ntey.) 



(2) In the middle of the inclosure is to be placed the thermo- 

 meter, upon which the heat of the sun is made to fall by means 

 of a hole in the inclosure, either with or without a lens. This 

 thermometer should be so constructed as to be readily susceptible 

 to solar influences. It is proposed to'make it of green glass (a 

 good absorber and radiator), and to give it a flattened surface in 

 the direction perpendicular to the light from the hole. Such an 

 instrument should be so adjusted as to receive the sun's light 

 continuously through the hole, and the objects of record would 

 be the simultaneous heights of the two thermometers, the one 

 giving the temperature of the inclosure, and the other of the 

 central thermometer. There are two conceivable methods by 

 which the necessary adjustment with regard to the sun's light 

 might be secured, namely, (a) the inclosure might be subject to 

 an equatorial motion so as to follow the sun, or (&) the inclosure 

 might be kept at rest and the solar rays kept upon the hole by 

 a heliostat. Capt. Abney is of opinion that the latter arrange- 

 ment is, mechanically, much preferable to the former. As the 

 direction of the earth's axis may be chosen as that into which 

 the sun's light is to be reflected, a heliostat of a very simple 

 construction will suffice ; and as the angle of incidence on the 

 minor of such a heliostat changes only very slowly with the 

 season, there is no difficulty in applying the small correction 

 required for the change in the intensity of the reflected heat 

 consequent on the change in the angle of incidence. It is 

 assumed that the mirror of the heliostat is a speculum. It has 

 been remarked by Gen. Strachey that some such instrument 

 as this now suggested, even if not made self-recording, would 

 have the advantage of giving an observation without the objec- 

 tionable necessity of putting the light on for a given time, and 

 then shutting it off, operations only suitable for trained ob- 

 servers. We think that it would be desirable to construct an 

 inclosure with its two thermometers such as herein recorded. In 

 all probability the loan of a heliostat and of an actinometer 

 might be obtained. By aid of the heliostat the sun's light might 

 be kept continuously upon the h le of the inclosure. The two 

 thermometers would be read, and the results compared with the 

 simultaneous reading of an ordinary actinometer. By such 

 means it is believed that the best method of constructing such an 

 instrument and observing with it might be found. We would 

 therefore ask for a continuance of our Committee, with the sum 

 of 30/. to be placed at our disposal for the purpose herein 

 specified. 



Report of the Committee, consisting of Mr. Sclaler, Mr. 

 Howard Saunders, and Mr. Tniselton Dyer (Secretary), ap- 

 pointed for the Purpose of Investigating the Natural History of 

 Timor Laut. — Since our last reporl was presented to the Asso- 

 ciation, Mr. Forties's botanical collection — which, from the result 

 of an unfortunate fire in the drying-house in which the Herbarium 

 had to be prepared, was very small, as he deplores — has been 

 handed over to the Royal Herbarium at Kew. Of this collec- 

 tion Sir Joseph Hooker, at a meeting of the Royal Geographical 

 Society on January 28, 1S84, made the following remarks : — 

 " From that time [of the appearance of Prof. Decaisne's 'Flora 

 Timoriensis '] to this, the limits of the Australian flora, so long 

 supposed to have been circumscribed with exactitude, have never 

 been laid down, though it has been enormously enlarged to the 

 north by the inclusion of the great island of Papua, which is to 

 a great extent Australian in its biology, ami by that of sundry 

 other islets to the north-east and north-west. It is under this 

 point of view that Mr. Forties's collections are so important. 

 It is true that for the most part they consist of what are 

 generally known as coral-island plants. . . . But besides this 

 there are some peculiar forms, and there are two plants of ex- 

 traordinary interest which I would simply instance as being 

 typical — one of the new Hebridean and one of the Australian 

 flora. It so happened that these two plants belonged to uni- 

 specific genera. . . . The existence of these plants pointed to 

 some old communication between these particular islands." No 

 detailed account of the ethnographical collection has yet been 

 published ; but as the collection has been deposited in the British 

 Museum, a description of the Timor Laut objects will doubtless 

 appear in the Catalogue of the Ethnological Department, while 

 the more interesting will be figured in Mr. Forties's forthcoming 

 volume At the last meeting of the Association at Southport, 

 Dr. J. G. Garson ("Report," p. 566) read a short account of the 

 crania (now in the British Museum) brought from Larat by Mr. 

 Forbes, which has been published in extenso in the Journal of 

 the Anthropological Institute, vol. xiii., and which concludes 

 with the following remarks on the relation of the inhabitants of 



